扭转模态导波检测管道纵向缺陷的数值模拟

为了评价超声扭转模态导波对管道纵向缺陷的检测能力,采用有限元方法进行了数值模拟研究.建立了带有纵向缺陷的管道有限元模型,激励和接收了扭转模态的T(0,1)导波,获得了缺陷长度与反射系数之间的关系曲线和回波信号在管道圆周方向的分布规律,并提出了采用T(0,1)模态导波检测时,对纵向缺陷进行周向和纵向定位的方法.结果表明,32.6 kHz的T(0,1)模态导波对管道上的纵向缺陷比较敏感,在缺陷所对应的圆周位置上,导波的回波幅度最大,而且,纵向缺陷对T(0,1)模态导波的反射系数呈单调增大、然后减小的趋势.

Numerical Simulation of Longitudinal Crack Detection in Pipes Using Ultrasonic Guided Wave T(0, 1) Mode

Numerical simulation of longitudinal crack detection in pipes using ultrasonic guided waves T(0,1) mode was made.A valid finite element model with longitudinally oriented through-thickness crack of various length was given,on which T(0,1)mode ultrasonic guided wave was excited.The results of numerical simu- lation showed the relation between longitudinal length and reflection coefficient which was defined as the am- plitude of the reflected signal divided by the amplitude of the incident signal as well as the circumferential distribution of reflected signal amplitude.Method to determine location of longitudinal and circumferentially locating crack using T(0,1)mode ultrasonic guided waves was also introduced.Simulation results show that T(0,1)mode is sensitive to longitudinal crack detection and the circumferential position where maximal reflection is received is the same with the circumferential position of longitudinal crack,as a whole,the reflection coefficient shows an increasing-decreasing tendency.